Tire retreading and repair materials



Patented July 10, 1951 UNITED STATES ATENT OFFICE Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Application January 21, 1949, Serial No. 71,861

4 Claims. 1 This invention relates to rubber repair materials or tire retreading strips such as Camelback, essentially composed of GR-S as distinguished from natural rubber.

tacky surface with terpene oils. However, reasons exist which make such a solution impractical.

It is desirable that tire tread stock have a high GR-S, as used herein, is a type of synthetic 5 degree of Wear resistance. Such a quality isv obrubber which may be described broadly as a rubtained by addition, in compounding, of reinforcbery copolymer of a conjugated diolen and a ing agents. A common example of suchan agent vinyl aromatic compound such as LS-butadiene is carbon black. But it has been found that natand styrene, butadiene and alpha methylstyrene, ural rubber and GR-S containing reinforcing butadiene and nuclearly chlorinated styrenes, and agents such as carbon black are relatively inthe like. compatible and form a very inferior product.

Tire retreading and rubber repair materials Tread stock composed entirely of GRS is less must necessarily have a surface of sufcient adwear resistant than one composed of natural rubhesiveness or tackiness to form a rm union (bom bei'. However, a tread stock composed of a mixduring preparatory processing and after vulcanl5 ture of GR-S and natural rubber is even less wear izing) with a tire body or other base. But good resistant by some twenty percent. Such a mixquality tread stocks being highly compounded ture is therefore commercially undesirable in with materials such as carbon black and zinc tire treads. f oxide, do not inherently have the requisite tacki- An object, therefore, of this invention is to ness. This is true whether such a stock is ccmproduce an essentially GR-S Camelback which posed of natural rubber or of GR-S. The former Will have a tacky surface Without the necessity of remedial practice involved laminating a calenlaminating a layer of celendered natural gum dered sheet of natural gum rubber on the face rubber uDOIl the face theleOf. of retieading strips. The gum rubber provided Another object of this invention is to produce the necessary tacky surface, an essentially GR-S Camelback or rubber repair A process was developed, hmvevery whereby a, material, Which Will have a tacky surface, by an tacky surface could be attained on natural rubmplOVed and Cheaper methOd. ber retread strips or repair materials more di- The foregoing and further Objects are Obtained rectly and with the consequent elimination of in the manner illustrated in the accompanying the above described laminating step. This proc 30 drawing, in Whichess is disclosed and claimed by Kempel in Patent Figure 1 iS a fragmentary View of a strip of N0 2,031,960, and provides generauy for the Camelback or rubber repair element essentially treatment of a face of an element of rubber, to be COHIDOSed 0f GR-S Which has a @Orner thereof used as repair or tire retreading material, with turned up 130 ShOW the tacky SurfaCe Obtained by a stable tei-pene on which is chiefly dipeutene practicing the present invention; and together with minor proportions of pinche, Figure 2 iS an enlarged sectional View taken terpiene, terpinolene and cymene. These oils ap- 011 line 2,2 0f Figure l. parenily form a solid solution with the rubber Similar numerals refer to Similar parte surface and in so doing the face thereof becomes hTOUghOLi'C the Several VeWS. highly tacky. 40 Referring to the drawing, I I is a rubbery strip Though the Kempel process 'is very successful Composed essentially of vulcanizable GR-S, I2 when used on repair elements composed of natis a face thereof, and I3 is a thin iilm of vulural rubber, it was found to be entirely inapcanizable rubber hydrocarbon having incorpoplicable when tried on GR-S materials. GrR-S rated therein a stable terpene oil. forms no solid solution with the terpene oils. It At a suitable stagein the preparation of the has, therefore, been necessary to continue the strip I I, as when it is being extruded from the old expensive practice, aforementioned, of lamitubing machine and While it is still Warm, the hating a layer of natural gum rubber on the face face i 2 is coated as by spraying or painting with 0f a GRS element in Order t0 provide e tacky a solvent cement composed of vulcanizable rubber surface thereon. hydrocarbon and the ordinary compounding in- When it became evident that the Kempel procgredients dissolved or dispersed in a rubber soless could not be utilized on GR-S as such, a natvent, e. g. gasoline. The strip II is dried by suitural solution of the problem seemed to be a comable means, thus depositing on I2 a thin film of bination of GR-S and natural rubber in a prorubber hydrocarbon. This rubber hydrocarbon .iportion or 1n proportions which would form a 5.3 nlm is transformed into the terpene containing film I3 by coating (as by spraying, painting or dipping) with a stable terpene oil, The result is a GR-S camelback with a Very tacky surface.

Major advantages of this invention are'. simplicity of operation and reduced production costs. The process is adapted to use with machinery and equipment conventional in the rubber industry With only minor adjustments. Since under previous practice the laminated sheet of gum rubber was a calendered sheet, it had to be of suicent thickness to permit the subsequent handling required to attach it on to the Camelback element. As a practical mattei' the limit to reduction in thickness of such a calendered sheet is about 0.020 inch. VThe customary K range is 0.025 to 0.031 inch. In contrast to the amount of gum rubber involved in carrying out such a laminating process, the film of gum rubber deposited from a rubber cement in practicing the present invention may be much thinner (0.002 to 0.007 inch). The saving represented thereby is substantial. In addition to reducing the amount of gum rubber used, the present invention also eliminates a manufacturing step requiring heavy machinery-that of calendering-with consequent production saying.

The invention is not limited to production of camelback alone but may be successfully practiced wherever one desires to produce articles essentially composed of vulcanizable GR-S which are to have surfaces adapted to adhering and vulcanizing to other rubbery surfaces, e. g. tube patching materials, rubber repair materials, and treads I for new tires.

essentially composed of a vulcanizable copolymer of 1,8-butadiene and styrene, and a thin film of vulcanizable natural rubber having incorporated therein a stable terpene oil, said lm being deposited on and attached to a face of the element.

2. A rubber repair material comprising a rubbery element essentially composed of a vulcanizable copolymer of a conjugated diolen and a styrene, and a thin im of vulcanizable natural rubber having incorporated therein a stable terpene oil, said lm being deposited on and attached to a face of the element.

3. Camelback comprising a rubbery element essentially composed of a vulcanizable copolymer of 1,3-butadiene and styrene and a thin film of vulcanizable natural rubber having incorporated therein a stable terpene oil, said film being deposited from a natural rubber cement on and attached to a face of the element.

4. Camelback comprising a rubbery element essentially composed of a vulcanizable copolymer of a conjugated diolefin and a styrene, and a thin hn of vulcanizable natural rubber having incorporated therein a stable terpene oil, said film being deposited on and attached to a face of the element.

ROBERT P. WHIPPLE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,031,960 Kempel Feb. 25, 1936 2,308,724 Starnberger Jan. 19, 1943 2,437,855 Leach Mar. 16, 1948 2,473,784 Carlin et al June 2l, 1949 OTHER REFERENCES du Ponts Blue Sheet BIJ-131, November 23, 1943, pages 1-3 by the Rubber Chem. Div. of the du Pont Co. 

1. CAMELBACK COMPRISING A RUBBERY ELEMENT ESSENTIALLY COMPOSED OF A VULCANIZABLE COPOLYMER OF 1,3-BUTADIENE AND STYRENE, AND A THIN FILM OF VULCANIZABLE NATURAL RUBBER, HAVING INCORPORATED THEREIN A STABLE TERPENE OIL, SAID FILM BEING DEPOSITED ON AND ATTACHED TO A FACE OF THE ELEMENT. 